This invention relates to a blind rivet made of a plastic material and used as a pin for uniting a plurality of superposed sheets or for fastening a part to a base plate or for serving as a leg by which a part is fastened to a base plate, and to a method for the manufacture of the rivet.
Usually, a blind rivet comprises a sleeve (female member) having a flange formed at one end thereof and a pin (male member) having at the leading end thereof a head of a diameter greater than the inside diameter of the sleeve. As disclosed by U.S. Pat. Nos. 3,178,989 and 3,230,818, for example, the male and female members of the blind rivet are separately fabricated from a malleable metal, such as aluminum alloy, copper alloy or mild steel, and they are assembled by having the pin inserted into the sleeve. U.S. Pat. No. 3,521,521 suggests the use of plastics for making blind fasteners. In actual use of this blind rivet, the pin is secured by the chuck of a tool and inserted through a perforation bored in a base plate subjected to riveting and then the pin is retrogressively extracted with the flange on the sleeve pressed fast against the base plate, causing the base plate to be tightened.
The metallic blind rivet is complicated to fabricate and, after fabrication, entails the extra work of assembling its male and female members. Each rivet thus assembled must be fastened to the chuck for the purpose of insertion and subsequent fastening. When the pin is drawn out to provide required tightening, the excess portion of the drawn pin must be cut off. With a view facilitating the severance of such excess portion of the drawn pin after the step of riveting, there has been suggested a rivet which is provided on the pin with a groove such that the pin is cut off along the groove automatically when the tensile force exerted on the pin reaches a definite magnitude (U.S. Pat. No. 3,230,818). With this rivet, however, there is a possibility that the pin will break before the rivet has provided perfect tightening of the base plate. No continuous riveting work can be attained, therefore.
To preclude possible release of the pin from the sleeve in the blind rivet of the foregoing description, there has been proposed a blind rivet of a plastic material wherein the pin has its leading end shaped in a bulbous form and the sleeve has its leading end shaped so as to accommodate said bulbous end of the pin so that, when the rivet is passed through the base plate and the pin is drawn out, the leading end of the pin is lodged fast within the sleeve to expand the wall of the sleeve outwardly, with said expansion providing required tightening of the base plate and preventing otherwise possible release of the pin from the sleeve.
The blind rivet of plastic material, however, has found virtually no acceptance because it fails to deform as designed, sustains breakage and, owing to elasticity, entails a possibility of the pin being pulled out of the sleeve after the step of tightening.
An object of the present invention is to provide a blind rivet of plastic material which provides infallible tightening and permits absolutely no possibility of the male member being released from the female member after the step of tightening.
Another object of this invention is to provide a blind rivet of plastic material which is easy to manufacture and is constituted by a complete assembly of a female member and a male member.
Still another object of the invention is to provide a blind rivet of plastic material which is easily mounted on the riveting tool and permits continued riveting operation.
It is also an object of this invention to provide a blind rivet of plastic material which allows for a wide variation in the thickness of base plates to be riveted and in the diameter of holes to be bored in said base plates for insertion of the rivet.
It is a further object of the present invention to provide an improved manufacturing method for making blind rivets of plastic material.